Justin Upton went 3 for 3 for Detroit, including a tiebreaking two-run single with two out in the seventh. Upton's big day helped make up for the loss of slugger Miguel Cabrera, who left after six innings due to left hip tightness.

Fulmer (8-6) allowed two homers for the first time this season. Justin Wilson pitched a perfect ninth for his ninth save.

San Francisco right-hander Matt Cain (3-8) surrendered five runs and seven hits in 6 1/3 innings. He dropped to 0-7 in nine starts since beating the Dodgers on May 15.

The Giants jumped in front on Hunter Pence's two-out solo homer over the out-of-town scoreboard in right-center in the first. The drive ended Fulmer's homerless streak at 73 2/3 innings — the longest active streak in the majors.

Martinez connected in the second and hit an RBI single in the fourth for a 2-1 Tigers lead. The next batter, Nicholas Castellanos, made it 3-1 with a sacrifice fly.

The Giants flew out to the warning track four times in the first four innings, but only managed two hits. Fulmer's command improved as the game went on, and he began to dominate in the middle innings.

But San Francisco rallied in the seventh. Brandon Belt doubled with one out and Brandon Crawford followed with a drive to right for his seventh homer, tying it at 3.

TRAINER'S ROOM

Giants: INF Eduardo Nunez (hamstring) was taking ground balls before the game. Nunez played one minor league game on June 30, but didn't feel comfortable. He's now undergoing treatment with the Giants and no return date has been set.

Tigers: OF Jim Adduci (oblique) is close to 100 percent, but will remain with Triple-A Toledo to continue getting at-bats and playing center field.

PAINFUL MEMORIES FOR TIGERS FANS

The Giants are the only team to clinch a World Series at Comerica Park, which opened in 2001. They finished off a four-game sweep of Detroit with a 4-3 win on Oct. 28, 2012.

UP NEXT

Giants: LHP Ty Blach (5-5, 4.60 ERA) will make the 14th start of his career in the second game of the series on Wednesday. Blach made his only interleague start on June 13, giving up seven runs to the Kansas City Royals in an 8-1 loss.

Tigers: RHP Daniel Norris (4-6, 5.00 ERA) pitches for the Tigers on Wednesday. He has never faced the Giants, but is 2-1 with a 4.58 ERA in five interleague appearances, including four starts.

Starting to rev things up, Hunter Pence has big night at plate and in left

Starting to rev things up, Hunter Pence has big night at plate and in left

PEORIA — Jeff Samardzija spent a couple minutes after Thursday’s start talking to reporters about how deep he thinks the Giants lineup can be. It’ll be a hell of a lot deeper if Hunter Pence keeps hitting like this.

After a slow start to the spring, Pence is charging. He had three hits against the Padres: a triple that bounced off the top of the wall in right-center, a hard single up the middle, and a double to center. The more encouraging plays for the Giants happened in left field. Pence chased down a drive to the line in the third inning, leaving the bases loaded. He opened the fourth by going the other direction and gloving a fly ball to left-center.

"A good game for Hunter, both ways," manager Bruce Bochy said. "He's getting more comfortable out there. You can see it with the jumps he's getting right now. It takes a little while when you change positions, but I think he's going to be fine out there."

The Giants appear set to have Austin Jackson and Pence atop the lineup against left-handed starters, and that duo could see plenty of time early. Seven of the first nine games are against the Dodgers, who have four lefty starters.

--- Evan Longoria had a double off the right-center wall on Wednesday after missing a week with a sore ankle. He had a single the same way in his second at-bat Thursday. More than the at-bats, Longoria has impressed with his soft hands and steady arm at third. The ankle looks fine, too.

--- It’s been a quiet spring for Andrew McCutchen, but we saw the wheels tonight. McCutchen easily stole second after a two-run single in the fifth. When Evan Longoria bounced one to the left side, shortstop Freddy Galvis tried to go to third for the lead out, but McCutchen beat that throw, too. He got up and put his hands on his hips, as if to say, "Why'd you even try that?"

--- Samardzija allowed three homers in a six-batter span in the third. He allowed three homers in an inning in his previous start, too, but he said he’s not concerned. Samardzija deemed it a sequencing issue. He’s working in a new changeup and threw it in situations he normally wouldn’t; Eric Hosmer took advantage of a floating one, crushing it to deep, deep right for the third homer.

--- With a runner on, Brandon Belt put down a perfect bunt to foil the shift. Belt does that every spring, particularly against NL West teams, but rarely during the regular season. Maybe this will be the year?

Belt later crushed a homer to deep right. That had to feel good for a number of reasons. Belt is fighting a cold and he learned earlier in the day that his college coach, Augie Garrido, had passed away.

Josh Osich goes back to his roots looking to unleash all the potential

Josh Osich goes back to his roots looking to unleash all the potential

The Giants Insider Podcast

SCOTTSDALE, Ariz. — For most pitchers, spring training is a time to experiment and add a pitch or two. Josh Osich is using this month to go the other direction.

Osich spent the offseason watching film of his 2015 season, when he looked like he might one day be the closer in San Francisco, and decided that he needed to get back to his roots. That means the curveball, which he tried so hard to mix in last year, is now far back in the cupboard. The four-seam and two-seam fastballs are once again the focus, with an emphasis on changing eye levels more than he did a year ago. The changeup and cutter will round out his arsenal for the most part.

Osich’s raw stuff is still as good as just about any lefty reliever in the league, and he hopes to take advantage of that while putting a rough 2017 season in his rearview mirror. He had a 6.23 ERA last season and 1.73 WHIP.

“It’s just one of those learning years,” Osich said. “I tried to live at the bottom of the zone and I was, but I was actually below the zone. So then I would fall behind and need to throw a strike and that’s when guys would hit me.”

Osich, 29, had a 2.20 ERA and 1.12 WHIP during that 2015 season that he keeps going back to. He walked eight batters in 28 2/3 innings, a far cry from the 27 he walked in 43 1/3 last year. While watching the 2015 version of himself, Osich saw that his hands were higher, and that’s something he’s working to replicate. He’s also trying to slow his pace to the plate. So far, the results are nothing but encouraging. Osich allowed one hit and struck out one in a 2 1/3 inning appearance on Wednesday night. Manager Bruce Bochy let him extend himself to keep the good vibes going.

In six appearances this spring, Osich has allowed just four hits over seven scoreless innings. He has seven strikeouts and one walk.

“O, it just seems like he’s got confidence,” Bochy said. “He’s kept it simple, he’s not tinkering with different pitches. He’s throwing more strikes, and more than anything he’s just trying to pound the strike zone now with quality strikes. That’s all he has to do. You look at him and he’s hitting 95 with a couple of good off-speed pitches. That works here.”